Themes: Improve performance of get_block_theme_folders function

This commit enhances the performance of the get_block_theme_folders function by introducing a new method called get_block_template_folders within the WP_Theme class. Previously, this function suffered from poor performance due to repeated file lookups using file_exists. The new method implements basic caching, storing the result in the theme's cache, similar to how block themes are cached in the block_theme property (see [55236]).

Additionally, this change improves error handling by checking if a theme exists before attempting to look up the file. It also enhances test coverage. 

Props spacedmonkey, thekt12, swissspidy, flixos90, costdev, mukesh27.
Fixes #58319.
Built from https://develop.svn.wordpress.org/trunk@56621


git-svn-id: http://core.svn.wordpress.org/trunk@56133 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/block-template-utils.php

@@ -37,22 +37,16 @@ if ( ! defined( 'WP_TEMPLATE_PART_AREA_UNCATEGORIZED' ) ) {
  * }
  */
 function get_block_theme_folders( $theme_stylesheet = null ) {
-	$theme_name = null === $theme_stylesheet ? get_stylesheet() : $theme_stylesheet;
+	$theme = wp_get_theme( (string) $theme_stylesheet );
-	$root_dir   = get_theme_root( $theme_name );
+	if ( ! $theme->exists() ) {
-	$theme_dir  = "$root_dir/$theme_name";
+		// Return the default folders if the theme doesn't exist.
-
-	if ( file_exists( $theme_dir . '/block-templates' ) || file_exists( $theme_dir . '/block-template-parts' ) ) {
-		return array(
-			'wp_template'      => 'block-templates',
-			'wp_template_part' => 'block-template-parts',
-		);
-	}
-
 		return array(
 			'wp_template'      => 'templates',
 			'wp_template_part' => 'parts',
 		);
 	}
+	return $theme->get_block_template_folders();
+}
 
 /**
  * Returns a filtered list of allowed area values for template parts.

wp-includes/class-wp-theme.php

@@ -194,6 +194,25 @@ final class WP_Theme implements ArrayAccess {
 	 */
 	private $cache_hash;
 
+	/**
+	 * Block template folders.
+	 *
+	 * @since 6.4.0
+	 * @var string[]
+	 */
+	private $block_template_folders;
+
+	/**
+	 * Default values for template folders.
+	 *
+	 * @since 6.4.0
+	 * @var string[]
+	 */
+	private $default_template_folders = array(
+		'wp_template'      => 'templates',
+		'wp_template_part' => 'parts',
+	);
+
 	/**
 	 * Flag for whether the themes cache bucket should be persistently cached.
 	 *
@@ -262,7 +281,7 @@ final class WP_Theme implements ArrayAccess {
 		$cache = $this->cache_get( 'theme' );
 
 		if ( is_array( $cache ) ) {
-			foreach ( array( 'block_theme', 'errors', 'headers', 'template' ) as $key ) {
+			foreach ( array( 'block_template_folders', 'block_theme', 'errors', 'headers', 'template' ) as $key ) {
 				if ( isset( $cache[ $key ] ) ) {
 					$this->$key = $cache[ $key ];
 				}
@@ -289,9 +308,11 @@ final class WP_Theme implements ArrayAccess {
 			}
 			$this->template               = $this->stylesheet;
 			$this->block_theme            = false;
+			$this->block_template_folders = $this->default_template_folders;
 			$this->cache_add(
 				'theme',
 				array(
+					'block_template_folders' => $this->block_template_folders,
 					'block_theme'            => $this->block_theme,
 					'headers'                => $this->headers,
 					'errors'                 => $this->errors,
@@ -308,9 +329,11 @@ final class WP_Theme implements ArrayAccess {
 			$this->errors                 = new WP_Error( 'theme_stylesheet_not_readable', __( 'Stylesheet is not readable.' ) );
 			$this->template               = $this->stylesheet;
 			$this->block_theme            = false;
+			$this->block_template_folders = $this->default_template_folders;
 			$this->cache_add(
 				'theme',
 				array(
+					'block_template_folders' => $this->block_template_folders,
 					'block_theme'            => $this->block_theme,
 					'headers'                => $this->headers,
 					'errors'                 => $this->errors,
@@ -345,6 +368,7 @@ final class WP_Theme implements ArrayAccess {
 			$this->cache_add(
 				'theme',
 				array(
+					'block_template_folders' => $this->get_block_template_folders(),
 					'block_theme'            => $this->is_block_theme(),
 					'headers'                => $this->headers,
 					'errors'                 => $this->errors,
@@ -378,6 +402,7 @@ final class WP_Theme implements ArrayAccess {
 				$this->cache_add(
 					'theme',
 					array(
+						'block_template_folders' => $this->get_block_template_folders(),
 						'block_theme'            => $this->block_theme,
 						'headers'                => $this->headers,
 						'errors'                 => $this->errors,
@@ -419,6 +444,7 @@ final class WP_Theme implements ArrayAccess {
 				$this->cache_add(
 					'theme',
 					array(
+						'block_template_folders' => $this->get_block_template_folders(),
 						'block_theme'            => $this->is_block_theme(),
 						'headers'                => $this->headers,
 						'errors'                 => $this->errors,
@@ -447,6 +473,7 @@ final class WP_Theme implements ArrayAccess {
 				$_child->cache_add(
 					'theme',
 					array(
+						'block_template_folders' => $_child->get_block_template_folders(),
 						'block_theme'            => $_child->is_block_theme(),
 						'headers'                => $_child->headers,
 						'errors'                 => $_child->errors,
@@ -467,6 +494,7 @@ final class WP_Theme implements ArrayAccess {
 					$this->cache_add(
 						'theme',
 						array(
+							'block_template_folders' => $this->get_block_template_folders(),
 							'block_theme'            => $this->is_block_theme(),
 							'headers'                => $this->headers,
 							'errors'                 => $this->errors,
@@ -489,6 +517,7 @@ final class WP_Theme implements ArrayAccess {
 		if ( ! is_array( $cache ) ) {
 			$cache = array(
 				'block_theme'            => $this->is_block_theme(),
+				'block_template_folders' => $this->get_block_template_folders(),
 				'headers'                => $this->headers,
 				'errors'                 => $this->errors,
 				'stylesheet'             => $this->stylesheet,
@@ -787,6 +816,7 @@ final class WP_Theme implements ArrayAccess {
 		$this->headers_sanitized      = null;
 		$this->name_translated        = null;
 		$this->block_theme            = null;
+		$this->block_template_folders = null;
 		$this->headers                = array();
 		$this->__construct( $this->stylesheet, $this->theme_root );
 	}
@@ -1714,6 +1744,37 @@ final class WP_Theme implements ArrayAccess {
 		return (array) apply_filters( 'site_allowed_themes', $allowed_themes[ $blog_id ], $blog_id );
 	}
 
+	/**
+	 * Returns the folder names of the block template directories.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @return string[] {
+	 *     Folder names used by block themes.
+	 *
+	 *     @type string $wp_template      Theme-relative directory name for block templates.
+	 *     @type string $wp_template_part Theme-relative directory name for block template parts.
+	 * }
+	 */
+	public function get_block_template_folders() {
+		// Return set/cached value if available.
+		if ( isset( $this->block_template_folders ) ) {
+			return $this->block_template_folders;
+		}
+
+		$this->block_template_folders = $this->default_template_folders;
+
+		$stylesheet_directory = $this->get_stylesheet_directory();
+		// If the theme uses deprecated block template folders.
+		if ( file_exists( $stylesheet_directory . '/block-templates' ) || file_exists( $stylesheet_directory . '/block-template-parts' ) ) {
+			$this->block_template_folders = array(
+				'wp_template'      => 'block-templates',
+				'wp_template_part' => 'block-template-parts',
+			);
+		}
+		return $this->block_template_folders;
+	}
+
 	/**
 	 * Enables a theme for all sites on the current network.
 	 *

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56620';
+$wp_version = '6.4-alpha-56621';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.